I opend my pool this year and shocked it as usual. After just a few days, a sandy substance appeared on the bottom and side walls of the pool liner. It cannot be brushed away. What is it, how did it happen and how can I correct it? Thanks in advance for any help that can be provided.

do you have a pool deck? What's it around the pool constructed? If you have rocky theme and decks accordingly, and is not fixed properly the sand could seep and settle in. I'm not sure though if the problem here is the same, but that is one possibility.

Next...sounds like a lateral is still either broken or not screwed in correctly because you hsould not still be getting sand in the pool from your return. Sand stuck in the impeller would be a first for me and I look at about 600 of them a year.

AS far as the cloudiness, if oyur chlorine level is correct then you may need to "Floc" the pool and then vacuum to waste.